Known processes for preparing pyrrolidinylacetamide derivatives include a process comprising reacting pyrrolidinylacetic acid or a reactive derivative thereof with an amine in an organic solvent in the presence of dicyclohexylcarbodiimide as disclosed in U.S. Pat. No. 4,341,790 and JP-A-56-2960 (the term "JP-A" as used herein means an "unexamined published Japanese patent application").
The above process is not suited for production on an industrial scale due to disadvantages, such as use of expensive dicyclohexylcarbodiimide as a condensing agent, involvement of complicated steps for separation and removal of dicyclohexylurea which is a by-product from dicyclohexylcarbodiimide, poor overall yield. Moreover, the starting material, e.g., 2-oxo-1-pyrrolidinylacetic acid, should be produced by reacting 2-pyrrolidinone with methyl bromoacetate and hydrolyzing the resulting methyl 2-oxo-1-pyrrolidinylacetate, and purified by distilling the reaction mixture under high pressure and at high temperature. These complicated operations and low yield are disadvantageous for industrial production.
On the other hand, a process for preparing N-substituted lactams is known as disclosed in British Patent No. 1,039,113. This known process comprises reacting an N-unsubstituted lactam with an alkali metal hydride and then reacting the resulting alkali metal derivative with an appropriate .omega.-chloroalkylamide. The chloroacetanilide derivative used in the process is prepared by a manner as disclosed, for example, in Yakugaku Zasshi (Pharmacological Journal), vol. 99(2), pp. 146 to 154 (1979), which comprises reacting xylidine with monochloroacetyl chloride in a glacial acetic acid to obtain 2,6-dimethylmonochloroacetanilide in a 78 to 80% yield. However, these processes are not still satisfactory from the viewpoint of yield on an industrial scale.